Contents lists available at ScienceDirect Diamond & Related Materials journal homepage: www.elsevier.com/locate/diamond Influence of seeding layer on photoelectrochemical hydrogen production over TiO 2 nanorod decorated with reduced graphene oxide Robabeh Bashiri a , Norani Muti Mohamed a,b, ⁎ , Liew Yi Ling c , Nur Amirah Suhaimi a , Muhammad Umair Shahid a,b , Suriati Sufian c , Chong Fai Kait b , Shuaib Mohamed Saheed b a Centre of Innovative Nanostructures & Nanodevices (COINN), Universiti Teknologi PETRONAS, 32610 Bandar Seri Iskandar, Perak, Malaysia b Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS, 32610 Bandar Seri Iskandar, Perak, Malaysia c Chemical Engineering Department, Universiti Teknologi PETRONAS, 32610 Seri Iskandar, Perak, Malaysia ARTICLE INFO Keywords: TiO 2 nanorod Reduced graphene oxide Anatase Rutile Photoelectrochemical cell Hydrogen ABSTRACT A seeded TiO 2 nanorod decorated with reduced graphene oxide (rGO) was synthesized to improve solar hy- drogen production performance in a photoelectrochemical cell. The rutile TiO 2 nanorod was grown on the surface of the screen-printed anatase TiO 2 /fluorine-doped tin oxide (FTO) substrate via hydrothermal technique and then rGO was deposited on the surface of seeded TiO 2 nanorod by spin-coating and thermal treatment. The photocatalytic activities are evaluated in terms of hydrogen production and photoelectrochemical properties. X- ray diffractometer and transmission electron microscopy show the presence of anatase and rutile TiO 2 with different lattice fringes and rGO on the surface of the photocatalyst. Field-emission scanning electron microscopy reveals that introducing seed layer increased the density of the nanorod and its active surface area. X-Ray photoelectron spectroscopy (XPS) and Raman spectra confirmed a strong interaction between TiO 2 and rGO, leading to better charge carrier transfers and reduce their recombination rate. The photocurrent density of seeded TiO 2 nanorod@ rGO was higher than rutile or anatase TiO 2 @ rGO due to low charge transfer resistance and long electron lifetime. The seeded TiO 2 nanorod@ rGO composites produced a maximum accumulative hydrogen of 1200 mmol/cm 2 in a mixture of 1 M KOH and 5 vol% glycerol in the photoelectrochemical cell under visible light irradiation compared with rutile or anatase TiO 2 @rGO. It is believed that this predominant photocatalytic activity is due to the synergistic contribution of direct electron transport between anatase and rutile TiO 2 phases, a high electron mobility of rGO and an increased surface area originated from TiO 2 nanorod. 1. Introduction Photoelectrochemical (PEC) water splitting over n-type TiO 2 has been reported by Honda and Fujishima in 1972 as a promising strategy towards energy and environmental sustainability. Many efforts have been devoted to designing suitable nanomaterials as photoanode in PEC cell to enhance solar hydrogen production performance [1,2]. Among various metal oxides, predominantly TiO 2 have been extensively stu- died for PEC water splitting due to its unique features such as low cost, nontoxicity, water stability and negative CB position. However, its predominant absorption in the UV region, low electron mobility and high charge recombination rate have negative impact on the photo- catalytic performance of TiO 2 [3,4]. Several attempts have been made to extend photoresponse of TiO 2 to visible light by reducing the bandgap energy through doping with metal and non-metal dopants, coupling with dyes and sensitizing with other semiconductors [5,6]. In recent years, the hybrid/composite of TiO 2 and carbon nanomaterials, particularly carbon nanotubes (CNTs) and graphene have attracted more attention. Graphene with an ar- ranged atomic sheet of sp 2 -bonded carbon atoms has been highlighted as a promising composite material with TiO 2 due to its high electronic conductivity and large specific surface area. These unique properties of graphene facilitate charge transportation and separation and increase reaction sites. Furthermore, introducing graphene on the surface of TiO 2 extend the light absorption range into visible region due to modification of the energy bandage by carbon [7,8]. Lim et al. [9] re- ported that incorporation of rGO on the surface of TiO 2 nanoparticle as an effective strategy enhance photocurrent response and stability compared to bare TiO 2 . In another work, Cui et al. [10] investigated the photocatalytic hydrogen evolution from water splitting over https://doi.org/10.1016/j.diamond.2019.03.006 Received 1 November 2018; Received in revised form 30 January 2019; Accepted 11 March 2019 ⁎ Corresponding author at: Centre of Innovative Nanostructures & Nanodevices (COINN), Universiti Teknologi PETRONAS, 32610 Bandar Seri Iskandar, Perak, Malaysia. E-mail address: noranimuti_mohamed@utp.edu.my (N.M. Mohamed). Diamond & Related Materials 94 (2019) 194–202 Available online 12 March 2019 0925-9635/ © 2019 Elsevier B.V. All rights reserved. T